Modern internal combustion engines include an exhaust gas recirculation line, which may be implemented both on the high-pressure side and also on the low-pressure side. In high-pressure-side exhaust gas recirculation, the combustion exhaust gas which flows out of the internal combustion engine is recirculated into an intake manifold section of an air supply system. In low-pressure-side exhaust gas recirculation, the combustion exhaust gas is removed from the exhaust gas discharge section after passing through a turbine of an exhaust-gas-driven turbocharger and returned to the intake side of a compressor of the turbocharger.
To comply with exhaust gas regulations, it is essential to know the physical variables which relate to the air supply system and the exhaust gas discharge section. In particular, determining and setting the exhaust gas recirculation rates of the low-pressure-side exhaust gas recirculation require the correct determination of the exhaust gas pressure and the gas mass flow on the low-pressure-side branching point in the exhaust gas discharge section. These variables may be measured with the aid of suitable sensors; however, suitable modeling of the physical variables is used to minimize the number of required sensors.